The invention relates to improvements in tamper-indicating closures as well as an integrally molded blank for the manufacture of a tamper-indicating closure.
Tamper-indicating closures for various types of containers are widely and numerously known and in use. These types of closure are mainly employed in the beverage and food industry for the most varied of uses. In order to hinder manipulation of such containers, mainly bottles, the closures are provided with a tamper-indicating band which is brought into engagement with a locking surface on the container neck. A protruding bead, one or more ribs, a groove or another shape for an undercutting on the container neck mostly serve as the locking surface.
One difficulty with the use of known closures is mainly that the tamper-indicating band on the one hand should slip over the container neck and locking surface easily and without damage to the frangible web or bridges connecting the band to the closure. In addition the tamper-indicating band must be elastic, in order to avoid too great a resistance when closing the bottle and, with that, damage to the frangible line.
On the other hand, the tamper-indicating band should be formed to be as stiff and resistant as possible, in order to reliably maintain engagement with the locking surface when opening the tamper-indicating closure, so that the tamper-indicating band will tear along the frangible line and thus display the initial opening.
These types of closures can be manufactured in one piece, together with the tamper-indicating band, by means of plastic injection molding. However, subsequent application of a weakened line to the closure blanks, between the closure cap and the tamper-indicating band, is also known. These types of devices and methods are known from U.S. Pat. No. 3,673,761 (Light/CibaGelgy), DE-OS-14 82 603 (Telllac/ALCA SA) or U.S. Pat. No. 4,895,265 (Luc et al./The West Co.).
However, tamper-indicating closures made of metal are also known on which a tamper-indicating band is subsequently affixed. The tamper-indicating element is, with that, normally annular in shape with a holding portion, with which it can be brought into interlocking connection with the closure cap. The holder portion-and with that the closure cap-is connected with the tamper-indicating band by means of connecting bridges or webs.
Other methods of manufacture of such tamper-indicating closures, such as compression molding, co-injection molding and similar, are also known.
A tamper-indicating band is known from U.S. Pat. No. 4,801,031 with which an inwardly folded tamper-indicating band possesses pleats in its end area, said pleats being directed inwards. On the one hand, this type of tamper-indicating band can be too stiff in its upper edge area, because the tamper-indicating band exists with its full material thickness between the individual fold-type protrusions. On the other hand, there is the risk that, during opening of the closure and thus with a vertical pressure being exerted onto the folds, the lower area of the tamper-indicating band will elastically yield and as a result the folds can slip over the retaining surface without tearing of the frangible line.
A closure is known from U.S. Pat. No. 4,470,513 (Ostrowsky/Ethyl Molded Products), the tamper-indicating band of which possesses a plurality of retaining elements which are provided with wedge shaped protrusions. It is apparent that such a closure can be further improved with reference to the stretching ability of the tamper-indicating band during initial placement and with reference to its engagement properties with the retaining surface.